Sweden has proof an enemy submarine was definitely in its waters last month, according to Reuters.
Sweden's military launched its biggest anti-submarine operation since the twilight of the Soviet Union on Oct. 17 after receiving what it said were credible eyewitness reports of some type of underwater craft in the archipelago that extends from the capital, Stockholm, into the Baltic Sea, Reuters reported.
The Svenska Dagbladet newspaper said Swedish military's analysis of findings during the hunt had yielded proof that at least one small foreign submarine was operating underwater, according to Reuters.
Prime minister says officials have "clear evidence" that a small submarine did illegally enter Swedish waters last month, sparking a week-long hunt, Reuters reported.
Officials do not know who was behind the incident, but the incursion into the Stockholm archipelago was "totally unacceptable," according to Reuters.
Military officials never blamed any country for the suspected intrusion, but Swedish defense analysts say Russia would be a likely culprit, Reuters reported.
The Swedish government and military declined to comment but a news conference with Prime Minister Stefan Lofven, the defense minister and the commander-in-chief of the Swedish military, is set for 5.30 a.m. ET, according to Reuters.
After the Oct. 17 incident, hundreds of troops, helicopters and stealth war ships searched the water for the submarine, or "under water activity," Reuters reported.